To show different prices, change product weight, or show a different image for each of your variants on Pinterest, you'll need to assign those values to each of your variant SKUs. See Adding Product SKUs for more information.

Recommendation on Inventory Tracking

For the best customer experience, we recommend utilizing inventory tracking for all products. Products with inventory tracking set to "none" will be sent to Pinterest as always being in stock, which may not align to your ability to quickly fulfill orders.